1. Field of the Invention
The present invention relates in general to steering systems for road vehicles and more particularly to a steering system of the type equipped with an anti-rotation mechanism for holding a steering wheel center pad and so on stationary irrespective of rotation of a steering wheel.
2. Description of the Prior Art
A steering system equipped with such an anti-rotation mechanism is disclosed, e.g. in Japanese Provisional Utility Model Publication No. 57-163448. The steering system includes a lower internal gear fastened with screws to an end of a steering column, an upper internal gear rotatably mounted on a hub portion of a steering wheel, and a pinion rotatably mounted on the hub portion and meshing with both of the internal gears so that the upper internal gear and the steering wheel center pad and so on mounted thereon are held stationary irrespective of rotation of the steering wheel.
A disadvantage of the prior art steering system is that in assembly of the steering system the lower internal gear cannot be subassembled to the hub portion of the steering wheel since the lower internal gear is designed so as to be fixedly attached to the steering column. For this reason, upon attachment of the hub portion of the steering wheel to the steering shaft, it is required to engage the pinion with the lower internal gear in such a manner that the upper internal gear, the steering wheel center pad and so on are placed in a predetermined angular position relative to the steering shaft, resulting in a difficult assembly work or a difficulty in locating the pad and so on in a predetermined angular position relative to the steering shaft.
Another disadvantage is the difficulty in axially aligning the upper and lower internal gears since they are designed to be mounted on different constituent parts, leading to a problem that if alignment of the upper and lower internal gears is not attained, play of the upper internal gear and the center pad, etc. mounted thereon will result to deteriorate the quality of the steering system.